Investigations were conducted to establish effects of fermentation and drying on the fermentation index （FI） and cut test of pulp pre-conditioned Ghanaian cocoa beans using a 4 x 3 full factorial experimental design...Investigations were conducted to establish effects of fermentation and drying on the fermentation index （FI） and cut test of pulp pre-conditioned Ghanaian cocoa beans using a 4 x 3 full factorial experimental design with the principal factors being pod storage （0, 3, 7 and 10 d） and fermentation time （0, 3 and 6 d） to study the changes occurring during the fermentation process. The study also used a 4 x 3 full factorial design with pod storage （0, 3, 7 and 10 d） and drying time （0, 3 and 7 d） being the principal factors investigated to study the changes occurring during the drying process. FI and cut test of the beans were studied during fermentation as well as the drying process. FI of the beans increased significantly with pod storage and fermentation but decreased slightly during drying. FI of the unfermented beans increased slightly from 0.674 for the unstored pods to 0.763 after 10 days of pod storage. The FI of the fermented beans （six days fermentation） also increased from 1.390 for the unstored pods to 1.424 for pods stored for 10 days. It decreased from 1.389 at the start of drying for the unstored pods to 1.105 for pods stored for 10 days at the end of drying （seven days）. FI of all the beans were however, above 1.0 at the end of fermentation and drying for all pod storage treatments. Cut test revealed that storage of pods for 3, 7 and 10 days increased the percentage of brown beans by 66%, 94% and 72%, respectively, by the sixth day of fermentation. Percentage of brown beans decreased to 61%, 76% and 63%, respectively, for pods stored for 3, 7 and 10 d at the end of drying （seven days）. Cocoa pods can be stored for up to 10 days, fermented for six days and dried for seven days with the necessary formation of brown pigments characteristics of well fermented and dried cocoa beans.展开更多
According to similarity theory, we carried out a dimensional analysis of the shearer drum correlation parameters and built similarity criteria. Based on these, similarity models of shearer drums were developed. Simult...According to similarity theory, we carried out a dimensional analysis of the shearer drum correlation parameters and built similarity criteria. Based on these, similarity models of shearer drums were developed. Simultaneously, based on an estab- lished cutting testbed of the coal and rock, cutting tests of different pick arrangements of the drum models were carried out, where the compressive strength of the analogous cutting material was 2.48 MPa and the drum rotary speed 67.5 r/min. The variance, the mean values, maxima and mean maxima of the torque load were analyzed for different type drum models. Moreover, the relation-ships between the type of pick arrangements and the cutting lump coal percentage were studied. The results indicate that the load fluctuation of the sequence drum is larger than that of the punnett square drum in the cutting process and the lump coal percentage and economic benefits of the sequence drum are inferior to the punnett square drum. We conclude that the punnett square drum is superior to the sequence drum.展开更多
This paper aims at reporting the results of a number of drag pick cutting tests on selected igneous rock samples to compare the experimentally determined maximum cutting force （FC） values with theoreti- cally estima...This paper aims at reporting the results of a number of drag pick cutting tests on selected igneous rock samples to compare the experimentally determined maximum cutting force （FC） values with theoreti- cally estimated ones. First, a review on theoretical rock cutting models proposed for both chisel and conical picks was presented in detail. Experimental study consists of both chisel and conical pick cutting tests in unrelieved （single-pick） cutting mode with varying cutting depths. FC＇ values were determined from experimental results, and theoretical models were utilized to compute FC for all cutting conditions. Computed and experimentally determined F（ data were then compared for a referenced cutting depth. It is shown that the theoretical models might overestimate or underestimate FC＇ and cannot give reliable results. Finally, explanations for these mismatches were presented.展开更多
The widespread utilisation of tunnel boring machines(TBMs)in underground construction engineering requires a detailed investigation of the cutter-rock interaction.In this paper,we conduct a series of largescale standi...The widespread utilisation of tunnel boring machines(TBMs)in underground construction engineering requires a detailed investigation of the cutter-rock interaction.In this paper,we conduct a series of largescale standing rotary cutting tests on granite in conjunction with high-fidelity numerical simulations based on a particle-type discrete element method(DEM)to explore the effects of key cutting parameters on the TBM cutter performance and the distribution of cutter-rock contact stresses.The assessment results of cutter performance obtained from the cutting tests and numerical simulations reveal similar dependencies on the key cutting parameters.More specifically,the normal and rolling forces exhibit a positive correlation with penetration but are slightly influenced by the cutting radius.In contrast,the side force decreases as the cutting radius increases.Additionally,the side force shows a positive relationship with the penetration for smaller cutting radii but tends to become negative as the cutting radius increases.The cutter's relative effectiveness in rock breaking is significantly impacted by the penetration but shows little dependency on the cutting radius.Consequently,an optimal penetration is identified,leading to a low boreability index and specific energy.A combined Hertz-Weibull function is developed to fit the cutter-rock contact stress distribution obtained in DEM simulations,whereby an improved CSM(Colorado School of Mines)model is proposed by replacing the original monotonic cutting force distribution with this combined Hertz-Weibull model.The proposed model outperforms the original CSM model as demonstrated by a comparison of the estimated cutting forces with those from the tests/simulations.The findings from this work that advance our understanding of TBM cutter performance have important implications for improving the efficiency and reliability of TBM tunnelling in granite.展开更多
This paper describes the application of orthogonal test design coupled with non-linear regression analysis to optimize abrasive suspension jet （AS J） cutting process and construct its cutting model. Orthogonal test ...This paper describes the application of orthogonal test design coupled with non-linear regression analysis to optimize abrasive suspension jet （AS J） cutting process and construct its cutting model. Orthogonal test design is applied to cutting stainless steel. Through range analysis on experiment results, the optimal process conditions for the cutting depth and the kerr ratio of the bottom width to the top width can be determined. In addition, the analysis of ranges and variances are all employed to identify various factors： traverse rate, working pressure, nozzle diameter, standoff distance which denote the importance order of the cutting parameters affecting cutting depth and the kerf ratio of the bottom width to the top width. ~rthermore, non-linear regression analysis is used to establish the mathematical models of the cutting parameters based on the cutting depth and the kerr ratio. Finally, the verification experiments of cutting parameters＇ effect on cutting performance, which show that optimized cutting parameters and cutting model can significantly improve the prediction of the cutting ability and quality of ASJ.展开更多
Through systematic cutting experiments, characteristics of the cutting performance of Ti(C, N) based cermets is identified. The experiments were designed to study their resistance,toughness, cutting force, tool-chip f...Through systematic cutting experiments, characteristics of the cutting performance of Ti(C, N) based cermets is identified. The experiments were designed to study their resistance,toughness, cutting force, tool-chip friction coefficient and machining quality by comparing them with those of WC based cemented carbides. The cutting data and the regressed empirical formulae would be useful to promote proper application of cermet cutting tool materials.展开更多
文摘Investigations were conducted to establish effects of fermentation and drying on the fermentation index （FI） and cut test of pulp pre-conditioned Ghanaian cocoa beans using a 4 x 3 full factorial experimental design with the principal factors being pod storage （0, 3, 7 and 10 d） and fermentation time （0, 3 and 6 d） to study the changes occurring during the fermentation process. The study also used a 4 x 3 full factorial design with pod storage （0, 3, 7 and 10 d） and drying time （0, 3 and 7 d） being the principal factors investigated to study the changes occurring during the drying process. FI and cut test of the beans were studied during fermentation as well as the drying process. FI of the beans increased significantly with pod storage and fermentation but decreased slightly during drying. FI of the unfermented beans increased slightly from 0.674 for the unstored pods to 0.763 after 10 days of pod storage. The FI of the fermented beans （six days fermentation） also increased from 1.390 for the unstored pods to 1.424 for pods stored for 10 days. It decreased from 1.389 at the start of drying for the unstored pods to 1.105 for pods stored for 10 days at the end of drying （seven days）. FI of all the beans were however, above 1.0 at the end of fermentation and drying for all pod storage treatments. Cut test revealed that storage of pods for 3, 7 and 10 days increased the percentage of brown beans by 66%, 94% and 72%, respectively, by the sixth day of fermentation. Percentage of brown beans decreased to 61%, 76% and 63%, respectively, for pods stored for 3, 7 and 10 d at the end of drying （seven days）. Cocoa pods can be stored for up to 10 days, fermented for six days and dried for seven days with the necessary formation of brown pigments characteristics of well fermented and dried cocoa beans.
文摘According to similarity theory, we carried out a dimensional analysis of the shearer drum correlation parameters and built similarity criteria. Based on these, similarity models of shearer drums were developed. Simultaneously, based on an estab- lished cutting testbed of the coal and rock, cutting tests of different pick arrangements of the drum models were carried out, where the compressive strength of the analogous cutting material was 2.48 MPa and the drum rotary speed 67.5 r/min. The variance, the mean values, maxima and mean maxima of the torque load were analyzed for different type drum models. Moreover, the relation-ships between the type of pick arrangements and the cutting lump coal percentage were studied. The results indicate that the load fluctuation of the sequence drum is larger than that of the punnett square drum in the cutting process and the lump coal percentage and economic benefits of the sequence drum are inferior to the punnett square drum. We conclude that the punnett square drum is superior to the sequence drum.
文摘This paper aims at reporting the results of a number of drag pick cutting tests on selected igneous rock samples to compare the experimentally determined maximum cutting force （FC） values with theoreti- cally estimated ones. First, a review on theoretical rock cutting models proposed for both chisel and conical picks was presented in detail. Experimental study consists of both chisel and conical pick cutting tests in unrelieved （single-pick） cutting mode with varying cutting depths. FC＇ values were determined from experimental results, and theoretical models were utilized to compute FC for all cutting conditions. Computed and experimentally determined F（ data were then compared for a referenced cutting depth. It is shown that the theoretical models might overestimate or underestimate FC＇ and cannot give reliable results. Finally, explanations for these mismatches were presented.
基金supported by the National Natural Science Foundation of China(Grant Nos.52278407 and 52378407)the China Postdoctoral Science Foundation(Grant No.2023M732670)the support by the Postdoctoral Fellowship Program of China Postdoctoral Science Foundation.
文摘The widespread utilisation of tunnel boring machines(TBMs)in underground construction engineering requires a detailed investigation of the cutter-rock interaction.In this paper,we conduct a series of largescale standing rotary cutting tests on granite in conjunction with high-fidelity numerical simulations based on a particle-type discrete element method(DEM)to explore the effects of key cutting parameters on the TBM cutter performance and the distribution of cutter-rock contact stresses.The assessment results of cutter performance obtained from the cutting tests and numerical simulations reveal similar dependencies on the key cutting parameters.More specifically,the normal and rolling forces exhibit a positive correlation with penetration but are slightly influenced by the cutting radius.In contrast,the side force decreases as the cutting radius increases.Additionally,the side force shows a positive relationship with the penetration for smaller cutting radii but tends to become negative as the cutting radius increases.The cutter's relative effectiveness in rock breaking is significantly impacted by the penetration but shows little dependency on the cutting radius.Consequently,an optimal penetration is identified,leading to a low boreability index and specific energy.A combined Hertz-Weibull function is developed to fit the cutter-rock contact stress distribution obtained in DEM simulations,whereby an improved CSM(Colorado School of Mines)model is proposed by replacing the original monotonic cutting force distribution with this combined Hertz-Weibull model.The proposed model outperforms the original CSM model as demonstrated by a comparison of the estimated cutting forces with those from the tests/simulations.The findings from this work that advance our understanding of TBM cutter performance have important implications for improving the efficiency and reliability of TBM tunnelling in granite.
基金supported by the Science and Technology Development Foundation of Shanghai Municipal Science and Technology Commission (Grant No.037252022)
文摘This paper describes the application of orthogonal test design coupled with non-linear regression analysis to optimize abrasive suspension jet （AS J） cutting process and construct its cutting model. Orthogonal test design is applied to cutting stainless steel. Through range analysis on experiment results, the optimal process conditions for the cutting depth and the kerr ratio of the bottom width to the top width can be determined. In addition, the analysis of ranges and variances are all employed to identify various factors： traverse rate, working pressure, nozzle diameter, standoff distance which denote the importance order of the cutting parameters affecting cutting depth and the kerf ratio of the bottom width to the top width. ~rthermore, non-linear regression analysis is used to establish the mathematical models of the cutting parameters based on the cutting depth and the kerr ratio. Finally, the verification experiments of cutting parameters＇ effect on cutting performance, which show that optimized cutting parameters and cutting model can significantly improve the prediction of the cutting ability and quality of ASJ.
文摘Through systematic cutting experiments, characteristics of the cutting performance of Ti(C, N) based cermets is identified. The experiments were designed to study their resistance,toughness, cutting force, tool-chip friction coefficient and machining quality by comparing them with those of WC based cemented carbides. The cutting data and the regressed empirical formulae would be useful to promote proper application of cermet cutting tool materials.
